1. Field of the Invention
The present invention generally relates to a safety apparatus for motor vehicles. In particular, the invention relates to a curtain air bag apparatus. During an emergency, such apparatus is constructed so that an air bag body is adapted to be inflated and deployed in a curtain shape that extends from a roof side-rail downwardly, thereby converting the interior side portion of a vehicle compartment.
2. Background Information
Air bag apparatus provided along a front-to-rear axis in the side portion of a vehicle compartment roof side-rail is typically known as a curtain airbag. In an emergency situation, such as a side collision or a rollover of the car, an air bag body is inflated and deployed in a curtain shape in the downward direction to protect a passenger located in a front and/or rear seats. In a crash situation, this deployment prevents direct contact of the passenger with the interior side-wall of the vehicle compartment, thus absorbing collision energy.
When not deployed, the air bag body is typically received in a folded state between the interior facing side of the vehicle roof side-rail and the interior roof trim. The interior roof trim serves to cover the air bag body, which is conveniently folded in a bellows shape. During an emergency, such as a vehicle side impact, a high-pressure gas is released into the air bag body from an inflator. This causes the air bag body to be deployed in a curtain shape along the interior side-wall of the vehicle compartment.
Curtain air bag constructions typically consist of a plurality of inflation chambers (bladders) arranged along the front-to-the rear axis of the vehicle body. The chambers are also usually linked to each other. These chambers are inflated individually by a high-pressure gas, thereby expanding to define the fully deployed air bag body, for example see Japanese Patent Application, Publication No. 2002-302006.
In conventional motor vehicles, however, the interior side-wall of the vehicle compartment where the air bag body is deployed is constructed mainly of side window glass, i.e., the front and rear side windows. A front pillar, a center pillar, and a rear pillar are also positioned respectively in the front part, the intermediate part, and the rear part of the side window glass. As will be appreciated, these structural pillars are necessary to define and strengthen the side-wall of the vehicle compartment as well as to support the roof. Typically, these structural pillars extend inwardly into the interior of the vehicle compartment so that the exterior of the vehicle appears to have a substantially planar surface. Hence, the interior surface of the side-walls of the vehicle compartment are typically non-planar and are somewhat contoured, with recesses formed where the side window glass is located between the structural pillars.
Known curtain air bags are designed to cover the entire side portion of the vehicle, from the front passenger side of the side window glass as far as the rear pillar. Such deployment is necessary to protect passengers in both the front and rear seats, particularly in the event of a side impact or rollover. The plurality of inflation chambers in the body of the air bag are, thus, disposed along the length of vehicle interior compartment including across the structural center and rear pillars. Therefore, when the specific chambers are inflated those located over the center and rear pillars will extend into the interior space of the vehicle compartment by the same amount as the pillars extend into the vehicle interior. This results in an uneven deployment configuration in which those inflation chambers located over the pillars deploy further into the vehicle interior compared to those inflation chambers positioned adjacent to the side window glass. Accordingly, when each chamber of the air bag body is fully inflated, the inflation force of the chambers overlaying the structural pillars causes those located adjacent to the side windows to be pulled further into the interior of the vehicle away from the side window glass.
The above description of traditional curtain air bag deployment can cause problems particularly when the passenger is moved in an outward direction (relative to the vehicle) as a consequence of a side collision or a rollover. Collision forces will move the passenger towards the side window glass, where the inflation chambers are spaced away from the side window glass and, thereby, the air bag will engage the passenger in the middle of air bag deployment. Hence, the air bag body fails to occupy the space between the passenger and the side window glass as intended and the protective effect of the curtain air bag is severely diminished.